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Rheological study of structural transitions in triblock copolymers in a liquid crystal solvent

Kempe, Michael D. and Verduzco, Rafael and Scruggs, Neal R. and Kornfield, Julia A. (2006) Rheological study of structural transitions in triblock copolymers in a liquid crystal solvent. Soft Matter, 2 (5). pp. 422-431. ISSN 1744-6848.

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Rheological properties of triblock copolymers dissolved in a nematic liquid crystal (LC) solvent demonstrate that their microphase separated structure is heavily influenced by changes in LC order. Nematic gels were created by swelling a well-defined, high molecular weight ABA block copolymer with the small-molecule nematic LC solvent 4-pentyl-4-cyanobiphenyl (5CB). The B midblock is a side-group liquid crystal polymer (SGLCP) designed to be soluble in 5CB and the A endblocks are polystyrene, which is LC-phobic and microphase separates to produce a physically cross-linked, thermoreversible, macroscopic polymer network. At sufficiently low polymer concentration a plateau modulus in the nematic phase, characteristic of a gel, abruptly transitions to terminal behavior when the gel is heated into its isotropic phase. In more concentrated gels, endblock aggregates persist into the isotopic phase. Dramatic changes in network structure are observed over small temperature windows (as little as 1 °C) due to tccche rapidly changing LC order near the isotropization point. The discontinuous change in solvent quality produces an abrupt change in viscoelastic properties for three polymers having different pendant mesogenic groups and matched block lengths.

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Kornfield, Julia A.0000-0001-6746-8634
Additional Information:© The Royal Society of Chemistry 2006 Received 12th January 2006, Accepted 23rd March 2006, First published on the web 4th April 2006 The authors acknowledge financial support from the AFOSR LC-MURI (f4962-97-1-0014), the ARCS foundation, the NSF Department of Materials Research (DMR-0216491), the NDSEG fellowship, and the James-Irvine Foundation. We would like to thank Steven Smith of Procter and Gamble for providing us with 1,2-polybutadiene samples, and María Lujan Auad for helpful discussions. M. D. K., R. V. and N. R. S. contributed equally to this work.
Issue or Number:5
Record Number:CaltechAUTHORS:KEMsoftm06
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:3920
Deposited By: Archive Administrator
Deposited On:19 Jul 2006
Last Modified:02 Oct 2019 23:08

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